Multipurpose breathing apparatus

ABSTRACT

A versatile closed-circuit breathing apparatus has a rectangular canister which is partitioned to provide for two separated volumes of CO2 absorbent. A mouthpiece, tubing and nonreturn valves, including a demand valve on the inhalation side, define a breath flow circuit in which exhalation passes through one volume of CO2 absorbent then through an expansible breathing bag and which is also a moisture trap and then back to the mouthpiece through the other volume of absorbent. Loss of effectiveness from moisture channelization is initially confined largely to one-half of the total volume of absorbent thereby providing for more uniform effectiveness over a long period of use. The construction is readily adaptable to a variety of uses including protection from contaminated atmospheres of various kinds, diving, resuscitation, decompression and medical uses.

United States Patent [72] Inventor Charles E.Michielsen 1120 CervantesWay, Paciiica, Calif. 94044 [21] Appl.No. 735,143 [22] Filed June6, 1968[45] Patented Apr. 20, I971 [54] MULTIPURPOSE BREATHING APPARATUS 3Claims, 5 Drawing Figs.

[52] U.S.Cl l28/l42.2, 55/482 [51] lnt.CI A62b7/04 [50] FieldofSearch128/142.2, 142,142.6,142.4,l45.8,188,19l;55/482,518

[5 6] References Cited UNITED STATES PATENTS 2,840,074 6/1958 Serra128/188 2,453,475 11/1948 Tobias 128/145.8 2,456,130 12/1948 Lambensen.128/l42.2 2,969,789 1/1961 Morch 128/l45.8 3,285,261 11/1966 Chaney...137/64 3,208,449 9/1965 Bartlett 128/145.8

ABSTRACT: A versatile closed-circuit breathing apparatus has arectangular canister which is partitioned to provide for two separatedvolumes of CO absorbent. A mouthpiece, tubing and nonretum valves,including a demand valve on the inhalation side, define a breath flowcircuit in which exhalation passes through one volume of CO absorbentthen through an expansible breathing bag and which is also a moisturetrap and then back to the mouthpiece through the other volume ofabsorbent. Loss of effectiveness from moisture channelization isinitially confined largely to one-half of the total volume of absorbentthereby providing for more uniform effectiveness over a long period ofuse. The construction is readily adaptable to a variety of usesincluding protection from contaminated atmospheres of various kinds,diving, resuscitation, decompression and medical uses.

PATENTEUAPRZOIH?! 3575,16?

I saw 1 BF 5 FlG 1 INVENTOR. CHARLES E. MICHIELSEN ATTORNEYS PATENTEU AmI971 3575.167

' sum 2 OF 5 INVENTOR. F I G 2 CHARLES E. MICHIELSEN 3 M4 Zq ATTORNEYSPATENTED'APR 2 0 |97| sum 3 BF 5 INVENTOR. CHARLES E. MICHIELSEN BY @MWW ATTORNEYS ATEN TE U 'APRZ 0 m SHEET U UF 5 v wE " INVENTOR. CHARLESE. MICHIELSEN I m; 1% ATTQRNEYS PATENT ED {PR2 01971 SHEEI 5 0F 5 m T NE V m CHARLES E. MICHIELSEN ATTOR N EYS IMIIUlL'IIWIUSE BREATHINGAPPARATUS Background of the Invention This invention relates to deviceswhich facilitate breathing under adverse conditions and moreparticularly to a breathing apparatus of the class capable of carrying acarbon dioxide absorbent material whereby the users exhalations may berecirculated and rebreathed.

Breathing apparatus of the kind used under water or in the presence ofsmoke or other atmospheric contaminations and for other purposes to behereinafter discussed may have. an open circuit or a closed-circuitbreath flow path. In open circuit apparatus, typified by certainunderwater breathing devices which are extensively used by skin divers,the user inhales breathable gas from a bottled supply and exhalesthrough a nonreturn valve to the ambient environment. These open circuitdevices are bulky and inefficient in a sense in that the user oftenabsorbs only about percent of the oxygen in each breath. Thus about 95percent of the oxygen which the user must carry in his bottle isultimately expelled and wasted.

To provide for more compact bottles and/or longer use times, a varietyof closed-circuit systems have been used. In this second class ofbreathing apparatus, the user exhales into a closed container and thenrebreathes essentially the same gas. This is made possible in aclosed-circuit device in that the gas flow between the users lungs andthe breathing bag is passed through a canister, containing a carbondioxide absorbent material and in that a small amount of oxygen from abottle is introduced into the system to replace the oxygen which isactually absorbed in the users lungs.

While prior closed-circuit breathing devices provide for relatively longuse periods in terms of the amount of oxygen which the user carries withhim. there have still been very serious problems which limit the periodof use and which tend to vary the effectiveness of the device in thecourse of a period of use. A prominent problem in this respect resultsfrom the effects of moisture on the CO absorbents normally employed inthese devices. Moisture is exhaled from the users lungs and the reactionby which CO is absorbed is itself a waterproducing one in addition tobeing exothermic. As a practical matter, the C0 absorbent becomesprogressively wetter in use and a phenomenon known as channelizationoccurs. Specifically, the granules of absorbent tend to fuse therebyshrinking the total absorbent volume and opening up channels throughwhich exhalation may pass without making adequate contact with theabsorbent. Thus the ability of the canister to remove the exhaled carbondioxide is progressively reduced. This is undesirable in that continuedbreathing of an atmosphere containing a greater than normal amount ofcarbon dioxide has adverse physiological effects. Further, prior closedcircuit devices provide replacement oxygen only to the extent that CO isabsorbed and any decrease in CO absorption results in a correspondingdecrease in oxygen content.

Moreover, closed-circuit breathing devices as heretofore constructedhave been subject to certain further problems including undesirably highbreathing resistance, structural complication, costly construction and alack of adaptability to uses other than the specific one for which thedevice was designed.

With respect to the latter factor, it should be noted that breathingapparatus of one kind or another may be employed in a variety ofdifferent situations in which environmental conditions are radicallydifferent. Such devices for example, are used by divers in underwateroperations and may also be used by firemen or other personnel who mustenter smokefilled buildings. In still other instances, a breathingapparatus may be used to carry out decompression procedures by personnelworking in a caisson or other highpressure environment. In still otherinstances, some form of breathing apparatus may be required to protectpersonnel exposed to toxic sprays or to a radioactively contaminatedatmosphere. Still other forms of breathing apparatus may be utilized asresuscitator for victims of heart attacks, electrical shock or othermedical emergencies which affect breathing. In general, these differentuse conditions have heretofore involved distinctively differentbreathing devices. Apparatus designed primarily for one of these useshas not tended to be readily adaptable to others thereof.

There are in fact so many different situations in which a breathingdevice can be useful, or absolutely necessary that it would be highlydesirable for such devices to be widely available in homes, offices,vehicles, first aid stations and many other locations. This has notheretofore been practical because of the cost, bulk and functionalspecialization of prior devices.

SUMMARY OF THE INVENTION This invention provides a compact efficient andversatile breathing apparatus for closed-circuit usage and is adaptablein addition to a variety of semiclosed circuit breathing applications.

As a closed-circuit device, the invention provides for longer useperiods and a more uniform effectiveness during such use periods in partby dividing the CO absorbent into two separate volumes along the breathflow circuit. In a preferred form, exhalation passes through a firstabsorbent volume and into a breathing bag and then back through theother absorbent volume to the mouthpiece or mask. As a consequence ofthe divided absorbent volume arranged in a series relationship, moistureaccumulation and the loss of effectiveness which results therefrom islargely confined to only a portion of the total absorbent during theinitial portion of a period of use. The second volume of absorbentremains near maximum effectiveness until such time as the first volumehas been fully utilized and then takes over the load with respect toremoving the CO from the exhaled breath. The breathing bag mayadvantageously be utilized as a watertrapping means in the flow pathbetween the two absorbent volumes for maximum protection of the secondvolume without excess bulk or structural complication.

In another aspect, the invention provides a flow circuit whereby thebreathing device may readily be interconnected with another such deviceor whereby a plurality of such devices may draw upon a common oxygensupply without interfering with the operation of each other.

The invention further provides a partitioned canister and breathing bagconstruction in which breathing resistance is desirably low and whichresults in a very compact and economically manufactured apparatus.

Accordingly it is an object of this invention to provide a breathingapparatus which remains highly effective over long periods of use inclosed-circuit applications and which is readily adaptable to variety ofsemiclosed circuit breathing functions.

It is a further object of the invention to provide a very compact,simple, reliable and economical breathing apparatus construction capableof usage under many different conditions and for a diversity ofpurposes.

The invention, together with further objects and advantages thereof willbest be understood by reference to the following description ofpreferred embodiments taken in conjunction with the accompanyingdrawings.

Brief Description of the Drawings In the accompanying drawings:

FIG. 1 is a frontal view of a closed-circuit breathing apparatusembodying the invention;

FIG. 2 is a cutaway exploded perspective view of the canister portion ofthe apparatus of FIG. 1 further illustrating the detailed constructionthereof;

FIG. 3 illustrates one method of carrying the apparatus of FIGS. I and 2on a user and further illustrates a highly advantageous technique forcoupling the breathing apparatus of two users in emergency situations;

FIG. 4 illustrates the adaptation of the apparatus of FIGS. 1 to 3 as anemergency resuscitator; and

FIG. 5 is a perspective view of a decompression chamber embodying theinvention whereby the hazardous accumulation of oxygen therein aheretofore encountered in such operations is prevented.

Description of Preferred Embodiments Referring now to FlGS. l and 2 ofthe drawings in conjunction, there is shown a closed-circuit breathingapparatus 11 having a canister 12 to which a majority of the othercomponents of the apparatus are attached. Canister 12 has a rectangularconfiguration in this example and in accordance with an important aspectof the invention, is partitioned into two chambers 13 and 14 to maintaina carbon dioxide absorbent material in two separate distinct volumes 16and 17.

To define the two chambers 13 and 14, the canister has a centralvertical partition 18. To provide for the input and removal of absorbentmaterial, a rectangular opening 19 is situated at the top of thecanister and spans the top edge of the central partition 18 with the topof the partition being situated slightly below the top of the canister.Canister 12 is normally closed by a conforming rectangular cover 21which fits over opening 19, the cover having apertures 22 which receiveupwardly extending threaded canister studs 23 with wing nuts 24 beingengaged on the studs to hold the cover in place.

To provide a fluidtight seal at the top of the canister and to maintaina small pressure on the granules of absorbent, a rectangular block ofsponge rubber or other suitable resilient material 26 fits into opening19 below cover 21 and is compressed by a conforming rectangular boss 27on the underside of the cover. Seal 26 contacts the top surface of bothabsorbent volumes l6 and 17 and for this purpose is provided with atransverse groove 28 on the underside to receive the upper edge ofcentral canister partition 18. Most CO absorbent materials shrink duringa period of use and this construction of the resilient seal 26 providesfor expansion of the seal as absorbent shrinkage occurs to prevent thedevelopment of excess void space in the absorbent volumes.

To provide for the recirculation of the user's exhalation as willhereinafter be described in more detail, the canister 12 is furtherprovided with a pair of rectangular openings 29 and 31 in the basethereof in chambers 13 and 14, respectively, adjacent the lower end ofcenter partition 18.

While the canister 12 may be formed of-a variety of materials,high-strength plastics, such as fibre glass for example, areparticularly desirable from the standpoint of low manufacturing cost.However most CO absorbent materials are arranged to change color astheir absorbent ability is used up to provide a visible warning to theuser. Accordingly, if an opaque material is used for the canister 12,transparent windows should be provided in the forward face or else theentire forward face should be formed of a transparent material such asLucite as in the present example.

Referring now to FIG. 1 in particular, further components of thebreathing apparatus 11 include a mouth piece 32 or a mask which may beof any of the various known constructions, the mouthpiece of the presentembodiment being of the type adapted to be held by the teeth of theuser. This form of mouthpiece has a transverse flow tube 33 whichtransmits exhalations and inhalations. A flexible exhalation side hose34 connects one end of tube 33 with a nonretum valve 35 which is securedto an elbow fitting 36 at the upper portion of the outer sidewall ofcanister 12 adjacent the previously described chamber 13 thereof.Nonretum valve 35 is a check valve of standard construction arranged tolimit gas flow between the mouthpiece 32 and canister 12 to a directiontowards the canister. Thus the user may exhale into the upper lateralregion of canister chamber 13 through valve 35 but a gas flow in areverse direction cannot occur.

To provide for the rebreathing of gas which has been reconstituted inthe canister 12, the opposite end of mouth piece tube 33 is coupled toan elbow fitting 37 at the center of the outer sidewall of canisterchamber 14 through a section of flexible hose 38 and an additionalnonretum valve 39. Nonretum valve 39 is in part a check valve arrangedto limit gas flow between canister chamber 14 and valve mouthpiece 32 toa direction towards the mouthpiece and to block flow in an oppositedirection. Valve 39 is also a demand regulator of the type which blocksgas flow toward the mouthpiece except at such times as inhalation by theuser generates a pressure decrease at the outlet side of the valveindicating that a gas flow is needed for the purpose of breathing. Thevalve 39 is further of the type provided with a bypass button 41 whichmay be depressed by the user's thumb to override the normal valvingaction and provide for a two-way flow passage between mouthpiece 32 andcanister 12 irrespective of pressure conditions. Suitable constructionsfor a nonretum demand regulator with manual bypass are known to the artand accordingly the detailed structure of valve 39 is not shown in FIG.1.

The above-described mouthpiece, valve and connecting hose structure thusprovides for the passage of the user's exhalations in canister chamber13 and through the CO absorbent 16 therein and out through opening 29 atthe base of such chamber and further provides a different inhalationflow passage wherein the gas to be inhaled is drawn through opening 31at the base of the canister into chamber 14 thereof and passes throughthe other CO absorbent volume 17 to return the mouthpiece throughfitting 37, valve 39 and hose 38. To provide for functioning of thesystem as a closed-circuit device wherein the exhalation is purified ofcarbon dioxide and rebreathed, a collapsible and expansible breathingbag 42 is utilized to receive the exhaled gas from canister opening 29and to maintain such gas available for inhalation through canisteropening 31.

The canister arrangement of the present invention provides for a verysimple and low-cost construction in what the breathing bag 42 may be aplastic sack of polyethylene film or other suitable flexible fluidtightmaterial having an open upper end which is simply fitted onto the lowerend of the canister 12. The bag 42 may be retained thereon in a verysimple manner by one or more elastic rings 43 which may, for example,conveniently be rubber 0 rings. Other forms of clamping means may besubstituted for the elastic rings 43 if desired. Referring now again toFIG. 2 in conjunction with FIG. 1, the canister 12 is preferablyprovided with grooves 44 around the lower portion thereof in which theelastic rings 43 may seat to forestall any movement of the rings on thecanister.

Accordingly, the user's exhalation passes into canister chamber 13,through the first absorbent volume 16 therein and then into thebreathing bag 42 which expands in response to the pressure. During thesubsequent inhalation, the gas trapped in bag 42 passes through thesecond canister chamber 14 and the additional separate absorbent volume17 therein and back to the mouthpiece 32 through valve 39. Thus with thesimple breathing bag 42 in place, the breathing apparatus is aclosed-circuit system in which the user rebreathes his own exhalationafter the carbon dioxide content thereof has been removed by theabsorbent 16 and 17.

As the use metabolizes a small portion of the oxygen in each breath in aclosed system of the present kind, it is usually necessary to provide asource of replacement oxygen or oxygen-containing gas mixture. For thispurpose, a conventional gas bottle 52 is provided and is coupled to afitting 53 at the forward face of canister 12 through a flexible hose54. Bottle 52 is provided with a manually adjustable metering valve 56and preferably with a gas pressure gauge 57 which provides an indicationof the amount of gas remaining in the bottle at any time.

Unlike prior closed-circuit breathing devices, the gas bottle 52 itselfneed not be provided with a demand valve as this function is performedby valve 39 which has been relocated as described above. In contrast toprior closed-circuit breathing devices, replacement oxygen iscontinually metered into the canister 12 through hose 54!- at a ratedetermined by the setting of valve 56. The disposition of a demand valvein the inhalation passage from the breathing bag to the mouthpiece inconjunction with a continuous flow of replacement oxygen provides foradvantageous interconnections of the breathing apparatus with other suchdevices as will hereinafter be discussed in more detail. For suchpurposes, the bottle 52 is further provided with an additional normallyclosed fitting 58.

The breathing apparatus III has some usages which do not require a gasbottle 52. Since the user metabolizes only a small portion of the oxygenin each breath, it is possible to breathe for a few minutes with thebottle 52 absent and fitting 53 capped. This provides an adequate periodfor certain uses of the apparatus. Use for emergency escape from acaisson or underwater craft is one such instance, If desired, a smalloxygen'containing capsule may be disposed in the breathing bag &2 in aposition where it can be broken by the users hands in an emergency.

Since a user may not be able to adjust the oxygen-metering valve 56 tomaintain a flow precisely similar to his rate of oxygen absorption,causing a pressure buildup in the flow circuit, a pressure relief valve46 of standard construction is situated at the forward face of canisterH2. Relief valve 46 is normally closed and opens in response to apredetermined pressure differential between the canister and theexternal environment to release gas from the canister to restore anapproximate equilibrium.

Canister i2 is further provided with pair of rings 59 along each side atthe back surface. Rings 59 engage with suitable harness means 61 asshown in FIG. 3 for carrying the apparatus on a users body, in front ofthe users chest in the present example. Preferably, the gas bottle 52 iscarried on the body by a separate harness strap 62. In the presentexample, the bottle 52 is shown carried on one hip of the user, which isa convenient position where the user must walk about such as in use by afireman entering a smoke-filled building. It will be appreciated thatother dispositions of the bottle 52 may be preferable in othercircumstances. In underwater usage, for example, the bottle 52 is moreadvantageously carried on the users back.

Referring again to FIGS. l and 2 in conjunction, the invention providesa disposition of the absorbent volume 16 and 117 within canister 1l2which has distinct advantages. In particular, within canister chamber 13the absorbent material 116 is retained between a pair spaced-apartrectangular screens 63 and 6 3 which slant with respect to the centralpartition 18. The innermost screen 64 has an upper edge adjacent thecenter partition l3 near the top of the chamber l3 and extendsdownwardly and slightly outwardly to engage the base of the canisteralong the outer edge of the opening 29 thereof. The other screen 63 hasa lower edge engaged with the base of the canister along the outsidecomer thereof and slants upwardly to the outer side of opening 19. Thescreens 63 and 64 should be formed by corrosion-resistant material andmay advantageously be thin stainless steel plates each having amultiplicity of small gas-pervious apertures 66. The absorbent material16 contained between the screens 63 and 64 may be of any of the knowntypes such an sodalime or barylime. The absorbent 17 within theinhalation side chamber M of the canister may be a similar material andis retained in an essentially similar manner by two additional spacedscreens 67 and 6b which have an opposite inclination. This configurationfor the two volumes of absorbent l6 and 17 and the associated screens63, 64, 67 and 68 thus defines a pair of oppositely tapered plenumregions in each of the canister chambers l3 and M at each side of thecorresponding absorbent volumes.

One result of the above-described canister and absorbent configurationis relatively low breathing resistance throughout a long period of use.Considering now still another advantageous feature, the two screens 63and 6d of chamber I13 are made slightly nonparallel and thus divergeslightly in the upward direction. The two screens 67 and 63 in chamber14 are similarly divergent. In general, the gas flow through theabsorbent volumes will tend to concentrate in a particular region oflowest resistance until the absorbent in that region becomes wetwhereupon the principal portion of the flow will shift to a dryeradjacent region. The varying thickness of the two absorbent volumes 16and 17 takes advantage of this effect in that the gas flow initiallytends to pass through the narrow lower portion of the absorbent volumesand shifts progressively upward as the breathing apparatus is used.

In use, the users exhalation passes through the absorbent 16 of canisterchamber 13; into the breathing bag 42 and is subsequently returned tothe mouthpiece 32 through the absorbent volume 17 of the canisterchamber 14 as described above. Due to the above-described constructionof the canister and breathing bag, the system remains effective for avery long period of use relative to prior closed-circuit devices. Animportant reason for this is the separation of the total volume ofabsorbent which is provided for by the described construction. Inparticular, a major cause of loss of effectiveness in carbon dioxideabsorbents is the progressive wetting of the absorbent material whichoccurs in part because the absorbing reaction is itself awater-producing one and is in part due to the moisture in the usersexhalation. The present construction takes advantage of a furtherphenomenon in carbon dioxide absorbing systems specifically the tendencyfor absorption to be concentrated in the first region of effectiveabsorbent which the gas flow encounters. Thus, in the present system,virtually the whole burden of absorbing carbon dioxide is performed bythe initial absorbent volume 16 during the first portion of the periodof use and the damaging effects of moisture accumulation are largelyconfined thereto. During this initial period, the second absorbentvolume I7 is largely inactive and retains maximum effectiveness untilsuch time as appreciable quantities of carbon dioxide begin to passthrough the first absorbent volume I6. At this point, the secondabsorbent volume 17 picks up the burden of absorbing carbon dioxide to aprogressively increasing extent. The net effect of this is that thetotal effectiveness of the system for absorbing CO is extended andremains more uniform throughout the extended period of use.

Considering now a further very advantageous feature of the invention, amoisture-trapping element is situated in the flow path between the twoabsorbent volumes l6 and 17 whereby moisture from the first absorbentvolume 16 is blocked to a considerable extent from reaching the secondabsorbent volume 17. This moisture trap is preferably defined by thebreathing bag 62 as in this example.

The CO absorbing reaction in the first absorbent volume 16 is exothermicin addition to being a water-producing one. It is inherent in the systemthat the gas expands and is cooled as it reaches the breathing bag 42from chamber 13. Further, under many operating conditions, the surfacesof the bag 42 are inherently cooler than the absorbent volume 16. Stillfurther, the configuration of the canister and breathing bag structurediscourages any direct flow of condensed moisture between absorbentvolumes l6 and 17. Because of these and other effects, the breathing bagconstitutes a fairly efficient water trap to forestall and reducemoisture damage to the inhalation side absorbent volume 17.

In addition to providing for long use periods with excellenteffectiveness, the above-described construction has further uniqueadvantages. It is an important object of the invention to provide apractical breathing apparatus which is not specialized to any specifictype of usage but which is adaptable to a wide variety of purposes. Theinvention has been described primarily with reference to use as aclosed-circuit breathing device. As such, it is usable as described forvirtually any situation in which the ambient environment around the usercannot be breathed either because of the lack of oxygen in usable formor because of the presence of substances which would have toxic effectsif inhaled. This includes use in diving,

use in the presence of atmospheres contaminated by smoke, toxic gases orsprays or airborne radiation of a harmful character and use at highaltitudes.

Further the breathing apparatus 11 is readily converted to a variety ofopen circuit or semiclosed circuit functions. With the breathing bag 42removed and the oxygen supply turned off or disconnected at fitting 53,the apparatus may be utilized where there is adequate oxygen in theexternal environment but where some environmental component must beblocked from the user's lungs as in gas mask applications. It will beapparent that the absorbent volumes l6 and 17 or only the absorbentvolume 17 on the inhalation side may be replaced with an air-purifyingmaterial suitable for the particular purpose. The plenum regions at eachside of chamber I4 may also be packed with an appropriate filtermaterial. This may, for example, be a carbon monoxide absorbent or inthe case of severe asthmatics a polon-filtering material may be disposedtherein. In the latter cases, the filtering charge may be treated withvarious medicinal substances known to be helpful if inhaled.

FIG. 4 illustrates still another essentially medical usage of thebreathing apparatus 11, specifically use as a resuscitator forindividuals whose natural breathing functions have been stopped orimpaired from some cause such as a heart attack, electrical shock or thelike. For this usage it is desirable, although not essential, that thebreathing apparatus ll be equipped with a mask 69 rather than thepreviously described mouthpiece and ideally a pressure gauge 71 iscoupled thereto to monitor the pressure in the victims lungs. With themask 69 in place, an operator need only rhythmically depress thebreathing bag 42 with one had while simultaneously depressing the bypassbutton 41 of inhalation side nonretum demand valve 39.

Referring now again to FIG. 3, still another advantageous property ofthe breathing apparatus 11 is illustrated. In particular, it is a simplematter to interconnect two of the breathing devices 11 so that one usermay draw upon the oxygen supply of the other in emergency situationswhere his own supply is exhausted or has failed for some reason oranother. This has not been practical in prior systems wherein a demandtype of valve is situated at the gas bottle rather than between thecanister and mouthpiece as in the present invention as pressureconditions in one such breathing apparatus may interfere with operationof the other. As a consequence, difficult expedients have been resortedto in emergency conditions such as passing the mouthpiece of onebreathing apparatus back and forth between two submerged divers.

To make the necessary interconnection a suitable length of flexible tube72 may be utilized with opposite ends being coupled to the previouslydescribed fittings 58 at the gas bottles 52 of the two separatebreathing devices I 1.

FIG. illustrates a related and highly useful application of theinvention to decompression procedures for personnel who work in acaisson or other high-pressure environment. As is well known, anindividual who has been subjected to high atmospheric pressure for anylength of time absorbs an excess of nitrogen in his blood stream andwill sufier from the bends, with possibly fatal consequence, if suddenlyreturned to a normal atmospheric environment. To forestall this result,such personnel customarily spend a period of time in a decompressionchamber 73 where they breath oxygen or a nitrogen-free mixture of oxygenand some other gas to clear the dissolved nitrogen from the bloodstream. There has been a serious risk associated with these operationsas heretofore conducted in that the worker inhales oxygen from a sourcewithin the decompression chamber and then exhales a large portion of theoxygen into the interior region of the chamber 73. One principal risk inthis procedure is the danger of a flash fire or explosion in theoxygenenriched atmosphere. This can easily occur from electrical sparksor other causes. FIG. 5 illustrates an adaptation of the inventionwherein decompression is carried out with no release of excess oxygeninto the interior of the decompression chamber.

In particular, each worker is provided with a closed-circuit breathingapparatus 11 in accordance with the invention. While the worker maydecompress while breathing from an oxygen bottle as hereinbeforedescribed provided the gas mixture in the bottle is relativelynitrogen-free, it is advantageous to remove the oxygen bottles from eachbreathing apparatus and to couple the gas input hose 54 thereof to acommon manifold conduit 74 within the chamber through which oxygen or asuitable mixed gas is supplied. A metering valve 76 is provided at eachoutlet along the manifold so that the worker may adjust his oxygenintake to the breathing apparatus. This arrangement is made practical inthat each breathing apparatus 11 contains its own demand valve asheretofore described.

It will be apparent from the foregoing that the present inventiondiffers from the various highly specialized breathing devices which itreplaces by being a highly adaptable multipurpose instrument which maybe kept available in many different places such as first aid stations,in vehicles, in the home, or on boats to serve a variety of verydifferent emergency situations which are related only in that the normalbreathing of individuals is affected in some way. It should further benoted that this is made practical for the first time by the constructionof the invention as described above wherein all principal elements whichare contacted by the users breath may be of a very simple and low-costconstruction. This includes the canister 12, breathing bag 42, nonretumvalves 34 and 39, mouthpiece 32 and the interconnecting tubing 38 andfittings 36 and 37. Each of these components are in face of sufficientlylow cost that aside from the gas bottle 52 and appertenances, it ispractical to treat the apparatus as a disposable item.

While the invention has been disclosed with respect to certain exemplaryembodiments, it will be apparent that many modifications are possibleand it is not intended to limit the invention except as defined in thefollowing claims.

Iclaim:

I. A breathing apparatus comprising:

an element engageable with a users mouth;

a partitioned canister having first and second chambers therein andhaving a pair of openings each communicating with a separate one of saidchambers;

means for retaining a separate charge of carbon dioxide absorbentmaterial in each of said chambers;

an exhalation nonreturn valve providing a one-way gas flow passage fromsaid mouth-engaging element to said first chamber of said canister;

an inhalation nonretum valve normally defining a one-way gas flowpassage from the second chamber of said canister to said mouth-engagingelement; and

an expansible breathing bag fitted onto the region of said canisterhaving said pair of openings to form a gas flow passage from said firstchamber of said canister to said second chamber thereof,

a disengageable cover for said canister providing for access to saidcharges of absorbent material, and

a layer of resilient material situated between said cover and saidabsorbent material of both of said chambers and compressed by engagementof said cover on said canister to maintain said absorbent material in apacked condition as shrinkage occurs.

2. A breathing apparatus comprising:

an element engageable with a users mouth;

a partitioned canister having first and second chambers therein, whereinsaid canister is of a substantially rectangular configuration and has acentral partition parallel to the two sidewalls thereof to define saidtwo chambers therein;

means for retaining a separate charge of carbon dioxide absorbentmaterial in each of said chambers; wherein said means for retaining saidcharges of absorbent material in said chambers comprise a pair ofspaced-apart gaspervious screens extending between opposite ends of theassociated chamber in an oblique relationship to said 9 ll) centerpartition where b y tapered plenum regions are an expansible breathingbag coupled to said canister and defined at opposite sides of each ofsaid charges of materdefining at least a portion of a gas flow passagefrom said ial in each of said chambers, first chamber of said canisterto said second chamber an exhalation nonreturn valve providing a one-waygas flow thereof.

passage f id mouthengaging element to Said fi t 3. A breathing apparatusas defined m claim 2 wherein said chamber f Said canister; pair ofscreens in each off said chambers are divergent in one an inhalationnonreturn valve normally defining a one-way d'mcmn y Sald charge ofabsol'benf matel'lal gas flow passage from the second chambar of Saidtherebetween of a nonuniform thickness along sald screens. canister tosaid mouth engaging element; and l 0

1. A breathing apparatus comprising: an element engageable with auser''s mouth; a partitioned canister having first and second chamberstherein and having a pair of openings each communicating with a separateone of said chambers; means for retaining a separate charge of carbondioxide absorbent material in each of said chambers; an exhalationnonreturn valve providing a one-way gas flow passage from saidmouth-engaging element to said first chamber of said canister; aninhalation nonreturn valve normally defining a one-way gas flow passagefrom the second chamber of said canister to said mouth-engaging element;and an expansible breathing bag fitted onto the region of said canisterhaving said pair of openings to form a gas flow passage from said firstchamber of said canister to said second chamber thereof, a disengageablecover for said canister providing for access to said charges ofabsorbent material, and a layer of resilient material situated betweensaid cover and said absorbent material of both of said chambers andcompressed by engagement of said cover on said canister to maintain saidabsorbent material in a packed condition as shrinkage occurs.
 2. Abreathing apparatus comprising: an element engageable with a user''smouth; a partitioned canister having first and second chambers therein,wherein said canister is of a substantially rectangular configurationand has a central partition parallel to the two sidewalls thereof todefine said two chambers therein; means for retaining a separate chargeof carbon dioxide absorbent material in each of said chambers; whereinsaid means for retaining said charges of absorbent material in saidchambers comprise a pair of spaced-apart gas-pervious screens extendingbetween opposite ends of the associated chamber in an obliquerelationship to said center partition whereby tapered plenum regions aredefined at opposite sides of each of said charges of material in each ofsaid chambers, an exhalation nonreturn valve providing a one-way gasflow passage from said mouth-engaging element to said first chamber ofsaid canister; an inhalation nonreturn valve normally defining a one-waygas flow passage from the second chamber of said canister to said mouthengaging element; and an expansible breathing bag coupled to saidcanister and defining at least a portion of a gas flow passage from saidfirst chamber of said canister to said second chamber thereof.
 3. Abreathing apparatus as defined in claim 2 wherein said pair of screensin each off said chambers are divergent in one direction whereby saidcharge of absorbent material therebetween is of a nonuniform thicknessalong said screens.